Many internal combustion engines include fuel injector assemblies. An injection pump pressurizes fuel, and the fuel injector assemblies inject the pressurized fuel into respective combustion chambers in the engine.
A typical fuel injector assembly includes an injection valve member having an injection nozzle at one end and an inlet connector supplying high-pressure fuel to the injection valve member. The injection valve member is generally cylindrical and has an axially uniform outer peripheral surface. The outer peripheral surface has a fuel inlet with a conical seat. The inlet connector, on the other hand, includes a fuel pipe and has a rounded joining surface at an outlet end.
The injection valve member is mounted in a mounting hole included in the engine cylinder head, and the inlet connector is mounted in a separate mounting hole. Once mounted, the axis of the inlet connector extends transversely to the axis of the injection valve member.
The inlet connector is coupled to the injection valve member by coupling the joining surface of the inlet connector to the fuel inlet of the injection valve member such that fuel can flow from the inlet connector, through the fuel inlet, and into the injection valve member.
More specifically, the inlet connector is laterally pressed into the valve body when interconnecting the inlet connector and the valve body. In so doing, a force directed transverse to the axis of the injection valve member is applied to the injection valve member. This transverse force can damage the fuel injector assembly by creating detrimental stress concentrations in the valve body.
Also, a relatively high force is typically needed for retaining the coupling of the inlet connector and the injection valve member. As a result, the valve body can be subjected to bending, which can damage the valve body. This problem is exacerbated as the fuel pressure is increased.
In partial response to this problem, U.S. Pat. No. 6,234,413 discloses an injector assembly with an injection valve member that is elliptical or polygonal in cross section. The injection valve member is mounted within a mounting hole having an inner surface that is circular in cross section. As such, the outer surface of the injection valve member abuts against the inner surface of the mounting hole at a plurality of “reaction points.” As such, these reaction points support the valve body against a force directed from the inlet connector toward the injection valve member. However, as shown in FIG. 2 of the '413 patent, a clearance exists at a circumferential point that is opposite to the axis of the inlet connector. As such, an inlet force directed from the inlet connector 9 toward the injection valve member 2 will create a plurality of reactive forces at the reaction points; however, the reactive forces are not directed along the same line as the inlet force. Accordingly, the injection valve member may be detrimentally affected by stress concentrations.
This problem is explained with reference to FIGS. 7A and 7B, which are pattern diagrams of a nozzle sliding portion of a conventional injector assembly. As shown in FIG. 7A, the axis Y of the injection valve member 2 is straight when the injection valve member 2 is uncoupled from the inlet connector 9. The injection valve member 2 abuts against the inner surface of the mounting aperture 71 at an upper support point A and a lower support point B. As shown in FIG. 7B, when the injection valve member 2 is coupled with the inlet connector 9, a coupling force F is directed along the axis of the inlet connector 9 toward the injection valve member 2. Supporting forces F′ result at the support points A, B. Because a moment arm exists between the coupling force F and the supporting forces F′, the valve body 2 is subjected to a bending moment, which causes the axis Y′ to curve. As such, the valve body 2 can be damaged due to bending.